The present invention generally relates to a method and apparatus for reforming a portion of an extrusion blow molded plastic container after molding and trimming, and more particularly to adding a three-dimensional feature or transferable element during the reforming of a portion of an extrusion blow molded plastic container after molding and trimming.
The process of extrusion blow molding plastic containers typically involves the steps of extruding a tube of monolayer or multilayer plastic material, capturing the tube between opposed mold sections, blowing the tube to the contours of the mold cavity, opening the mold, removing the container, and trimming the end of the container neck finish. This trimming operation can involve removal of a flash or moil from the neck finish. The trimmed material may be scrapped or, alternatively, recycled as process regrind. In another exemplary extrusion blow molding operation, the trimming operation can involve separation of two containers that are molded end-to-end. In either case, the trimming operation can leave an uneven end surface for later sealing engagement with a container closure. Furthermore, the end surface of the container neck finish may have mold parting line seams that can deleteriously affect sealing engagement with a container closure. These uneven or inconsistent end surface features can also affect induction sealing. Induction sealing can typically involve induction welding a metallic liner disk to a container end surface after filling the container to obtain a satisfactory container seal.
In order to correct these unwanted features, it has been proposed to burnish the end surface of the container neck finish by contacting the neck finish end surface with a heated burnishing tool. Upon contacting the container neck finish end surface, the tool simultaneously heats the end portion of the neck finish to a particular softening temperature of the plastic material and modifies the end surface to eliminate mold parting line seams, uneven trim portions and other post-molding imperfections. This process, however, has certain disadvantages. For example, the heated plastic of the container neck finish may tend to stick to the heated burnishing tool. It is also difficult to control the temperature of the burnishing tool so as to obtain a desired temperature at the burnishing surface of the tool. Moreover, effective burnishing often requires that one of the bottle or the burnishing tool be rotated relative to the other to achieve a desired effect. This introduces additional process variables and, consequently, affects production speed. Thus, the tendency of the heated plastic to stick to the burnishing tool, in combination with the oft-required rotational step and difficulty of controlling the burnishing surface temperature of the tool, makes it difficult to determine and control the optimum tool-to-surface contact time (i.e., dwell time). The dwell time, during which the burnishing tool is in contact with the end portion of the neck finish, as well as additional process variables, should be minimized to achieve desired production speeds.
Additionally, there is no known technique for adding unique three-dimensional features during modification of a molded and trimmed portion of a container to provide a means for detecting counterfeit containers and/or to alter the aesthetic appearance of the container. Likewise, there is no known technique for adding a transferable element to a container during modification of a molded and trimmed portion of a container. Such a transferable element can serve to alter the aesthetic appearance of the container. It can also provide a means for detecting counterfeit containers and/or allow more effective and efficient tracking of the respective container. In the past, tracking of individual containers was generally performed by way of a unique bar code identifier symbol printed on a label attached to a respective container. Tracking using bar coded labels, however, can require specific container orientation for proper scanning which introduces additional process variables.